The present invention relates to a copier, facsimile transceiver or similar image forming apparatus.
An image forming apparatus such as a copier usually uses an electrophotographic process or cursor process for forming a visible image on a recording medium which is implemented as a sheet. The visible image is formed by fine particles of toner stored in a developing device and sequentially consumed due to repetitive image formation. The problem with this type of image forming apparatus is, therefore, that a toner has to be supplied every time the amount of toner existing in the developing device becomes short. The supply of toner is the most troublesome operation regarding the maintenance of the apparatus.
While various kinds of toner supply methods have heretofore been proposed, typical of conventional methods are one which directly supplies a toner to a toner supply section included in a developing device, and one which supplies a toner from a toner cartridge which is removably mounted on the toner supply section. The cartridge scheme is disclosed in, for example, Japanese Patent Laid-Open Publication No. 188171/1988. This Laid-Open Publication teaches a procedure in which the operator loads the toner supply section of a developing device with, among a plurality of toner cartridges, a cartridge having the largest size first. As the toner cartridge becomes empty due to the supply of toner, the operator inserts a new toner cartridge smaller than the largest toner cartridge into the latter. When the smaller toner cartridge is emptied, the operator inserts another new toner cartridge even smaller than the empty toner cartridge into the latter. This frees the operator from the need for removing a toner cartridge from the toner supply section of the developing device every time it becomes empty. However, since some toner still remains in the empty cartridge left in the toner supply section, it is likely that the insertion of a new cartridge into the empty cartridge generates a stream of air to scatter around the remaining toner to the outside through the opening of the empty cartridge. To eliminate this problem, the empty cartridge may be automatically transported from the toner supply section to a cartridge collecting section remote from the toner supply section by a transporting device, as disclosed in Japanese Patent Application No. 286418/1990 by way of example. Such a system not only prevents the toner remaining in the empty cartridge from being scattered around but also promotes easy and efficient handling of cartridges. However, the prerequisite with this kind of approach is that the extra section for collecting empty cartridges be as small as possible since the space available in the apparatus is limited.
On the other hand, it is a common practice with the above-described type of image forming apparatus to remove a toner remaining on a photoconductive element and collect it in a waste or used toner bottle which is mounted on the apparatus. The toner bottle has to be discarded when filled with the waste toner and before it becomes full. Further, the photoconductive element itself has to be replaced from time to time since it deteriorates due to aging and has the surface thereof scratched or otherwise damaged due to repetitive image formation. In this manner, the maintenance of an image forming apparatus includes various operations which are troublesome to perform.
To facilitate the maintenance of an image forming apparatus, i.e., supplying a toner, discarding a waste toner and replacing a photoconductive element, the photoconductive element and the waste toner bottle and toner supply section arranged around the element may be constructed into a unit which is bodily replaceable, as also proposed in the past. Although this approach makes it needless to, for example, replace a toner cartridge every time the cartridge becomes empty, it forces even a developing roller, charger, cleaning blade and other components which are still usable to be discarded when the cartridge becomes empty. That is, such a unit scheme is not practicable without wasting many parts which are still usable. While easy maintenance is one of extremely important factors from the product standpoint, discarding usable parts is not desirable when it comes to the effective use of limited resources.